Abstract
We investigated the measurement system of internal voids in impression material using a digital image analyzer explained in previous paper.
In this paper, we investigated the influence of the difference of impression material and mixing method on internal voids.
Nine impression materials were used to evaluate internal voids. They were mixed and injected into a cylindrical plastic ring. After setting, disk specimens were made by cutting them into a same thickness. Area and the number of internal voids that emerged on the surface of specimen were measured.
Quantitative measurement of fine internal voids was made possible by using the digital image analyzer. Each impression material had a large number of internal voids which were less than 0.025mm2. In hand mixing, there were significant differences among impression materials with regard to the area and number of internal voids. Alginate impression material had the maximum value and medium-viscosity polyvinyl silycone elastomer had minimum value. Viscosity of impression material was correlated with the distribution of internal voids. In mechanical mixing, the number of internal voids increased slightly and the area decreased significantly in comparison with hand mixing. Using a syringe caused internal voids even in a void-free impression material. Internal voids were produced by mixing more than by the syringe.
